Handling face discontinuities in 360-degree video coding

ABSTRACT

Systems, methods, and instrumentalities may be provided for discounting reconstructed samples and/or coding information from spatial neighbors across face discontinuities. Whether a current block is located at a face discontinuity may be determined. The face discontinuity may be a face boundary between two or more adjoining blocks that are not spherical neighbors. The coding availability of a neighboring block of the current block may be determined, e.g., based on whether the neighboring block is on the same side of the face discontinuity as the current block. For example, the neighboring block may be determined to be available for decoding the current block if it is on the same side of the face discontinuity as the current block, and unavailable if it is not on the same side of the face discontinuity. The neighboring block may be a spatial neighboring block or a temporal neighboring block.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/560,992, filed Sep. 20, 2017, U.S. Provisional Application Ser.No. 62/622,551, filed Jan. 26, 2018, U.S. Provisional Application Ser.No. 62/625,575, filed Feb. 2, 2018, and U.S. Provisional ApplicationSer. No. 62/628,752, filed Feb. 9, 2018, the contents of which areincorporated by reference herein.

BACKGROUND

Virtual reality (VR) is being applied in many application areasincluding, but not limited to, healthcare, education, social networking,industry design/training, games, movies, shopping, entertainment, and/orthe like. VR may enhance the viewer's experience, for example, bycreating a virtual environment surrounding the viewer and generating atrue sense of ‘being there’ for the viewer. A VR system may supportinteractions through posture, gesture, eye gaze, voice, etc. The systemmay provide haptic feedback to the user such that the user may interactwith objects in the VR environment in a natural way.

SUMMARY

Systems, methods, and instrumentalities may be provided for discountingreconstructed samples and/or coding information from spatial neighborsacross face discontinuities. Whether a current block is located at aface discontinuity may be determined. The face discontinuity may be aface boundary between two or more adjoining blocks that are notspherical neighbors. The coding availability of a neighboring block ofthe current block may be determined, e.g., based on whether theneighboring block is on the same side of the face discontinuity as thecurrent block. For example, the neighboring block may be determined tobe available for decoding the current block if it is on the same side ofthe face discontinuity as the current block, and unavailable if it isnot on the same side of the face discontinuity. The neighboring blockmay be a spatial neighboring block or a temporal neighboring block.

Determining that the current block is located at the face discontinuitymay be based on a face discontinuity indication in a bitstream. The facediscontinuity indication may be an indication that a face boundary is adiscontinuous face boundary. The face discontinuity indication may be anindication of two or more endpoints of the face discontinuity. The facediscontinuity indication may be an indication of frame-packinginformation.

A decoding function may be performed on the current block, for examplebased on the coding availability of the neighboring block. The decodingfunction may include deriving a merge mode for the current block. Forexample, if the neighboring block is determined to be available, theneighboring block may be added to a merge candidate list (e.g., a listof candidate blocks). The neighboring block may be excluded from themerge candidate list if the neighboring block is determined to beunavailable. The decoding function may be, for example,inter-prediction, intra-prediction, cross-component linear modelprediction, overlapped block motion compensation, a deblocking filter, asample adaptive offset filter, or an adaptive loop filter.

The coding availability of a reconstructed sample may be determined,e.g., based on whether the reconstructed sample is on the same side ofthe face discontinuity as the current block. For example, thereconstructed sample may be determined to be available for decoding thecurrent block if it is on the same side of the face discontinuity as thecurrent block, and unavailable if it is not on the same side of the facediscontinuity. An unavailable reconstructed sample may be replaced withone or more available reconstructed samples. A template that containsthe unavailable reconstructed sample may be marked as unavailable.

A current block may be crossed by a face discontinuity. The currentblock may be split into two or more prediction units (PUs). The PUs maybe separated by the face discontinuity. Motion compensation may beperformed separately for each PU.

Performing a decoding function on the current block based on the codingavailability of the reconstructed sample may include applying one ormore of cross-component linear model prediction, overlapped block motioncompensation (OMBC), a deblocking filter (DBF), a sample adaptive offset(SAO) filter and/or an adaptive loop filter (ALF).

Face discontinuities in frame-packed picture may be identified, forexample based on a face discontinuity indication signaled in abitstream. In examples, the face discontinuity indication may includeframe-packing information that identifies edges corresponding to facediscontinuities. In examples, the face discontinuity indication mayinclude an indication of whether a boundary between two faces iscontinuous or discontinuous. In examples, the face discontinuityindication may include an indication of the endpoint coordinates of aface discontinuity. The determination and/or signaling of facediscontinuities may be performed.

For intra and inter prediction, if a block is located on the right sideof a face discontinuity, the left, above left, and below leftframe-packed neighbor blocks may be located on the other side of theface discontinuity and may be considered as unavailable for inferringattributes, e.g., for deriving the most probable mode in the intraangular process, for deriving the merge mode in inter prediction, and/orfor motion vector prediction. Similar considerations may be applied to acurrent block which may be located on the left side of, above, and/orbelow a face discontinuity. The coding availability of spatialcandidates at face discontinuities may be determined.

For intra and inter prediction, if a block is located on the right sideof a face discontinuity, the reconstructed samples located on the leftside of the block may be located on the other side of the facediscontinuity and may not be correlated with the current block samples.In this case, the reconstructed samples may be considered as unavailablein one or more prediction approaches, e.g., DC, planar, and/or angularmodes in intra prediction, Frame Rate Up Conversion (FRUC) template modeand local illumination compensation (LIC) mode in inter prediction.Similar considerations may be applied to a current block that is locatedon the left side of, above, and/or below a face discontinuity. Thecoding availability of reconstructed samples at face discontinuities maybe determined.

For cross-component linear model prediction, reconstructed samples atface discontinuities may be discarded if they are not located on thesame side of a face discontinuity as the current block. For example, ifa block is located on the right side of (or below) a face discontinuity,the reconstructed samples located on the left side of (or above) theface discontinuity may be discarded for estimating the parameters of thelinear model. Derivation of the linear model parameters may beperformed.

The template on a side of a face discontinuity may be discarded for aDIMD search. For example, if a block is located on or near the rightside of (e.g., below) a face discontinuity, and part or all of thesamples from the left (e.g., top) template and/or part or all of thesamples from the left (e.g., top) reference samples used to predict theleft (e.g., top) template are located on the other side of the facediscontinuity, the template on the other side of the discontinuity maybe discarded for a DIMD search. The usage of the top and left templatesnear face discontinuities in DIMD may be determined.

For OBMC, if the current block (or sub-block) is located on the rightside of a face discontinuity, the adjustment of the first columns of thecurrent block (or sub-block) using the motion vector of the right block(or sub-block), which is located on the other side of the facediscontinuity, may be skipped. Similar considerations may be applied toa current block (or sub-block) which is located on the left side of,above, and/or below a face discontinuity. OBMC-based adjustment of(blocks (or sub-blocks) at face discontinuities may be performed.

For DBF, if a vertical (or horizontal) block boundary is within theproximity of a vertical (or horizontal) face discontinuity such that oneor more (e.g., all) samples used in the DBF filter are not located onthe same side of the face discontinuity, DBF may be disabled across theblock boundary. Deblocking across face discontinuities may be performed.

For SAO, if the current sample is located on the right side of a facediscontinuity, the horizontal and two diagonal categories in the edgeoffset mode may be disabled for that sample position, as a sample usedin gradient based classification may be located on the other side of theface discontinuity and may not be correlated with the current sample.Similar considerations may be applied to a current sample which islocated on the left side of, above, and/or below a face discontinuity.The SAO process at face discontinuities may be performed.

For ALF, if a current luma (or chroma) sample is located within four (ortwo) samples from a face discontinuity, ALF may be disabled for thatsample location, as one or more samples used in the 9×9 (or 5×5) diamondfilter may be located on the other side of the face discontinuity andmay not be correlated with the current sample. ALF may be performed atface discontinuities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) illustrates an example sphere sampling along a longitudedirection and a latitude direction in an equirectangular projection(ERP).

FIG. 1(b) illustrates an example 2D planar in ERP.

FIG. 1(c) illustrates an example picture produced using ERP.

FIG. 2(a) illustrates an example 3D geometry structure in a cubemapprojection (CMP).

FIG. 2(b) illustrates an example 2D planar with 3×2 frame-packing andsix faces.

FIG. 2(c) illustrates an example picture produced using cubemapprojection.

FIG. 3 illustrates an example 360-degree video processing.

FIG. 4 illustrates a block diagram of an example block-based encoder.

FIG. 5 illustrates a block diagram of an example block-based decoder.

FIG. 6 illustrates an example of using reference samples in highefficiency video coding (HEVC) intra prediction.

FIG. 7 illustrates example indications of intra prediction directions inHEVC.

FIG. 8 illustrates examples of spatial neighbors used for deriving themost probable modes in the HEVC intra angular process.

FIG. 9 illustrates an example inter prediction with one motion vector(uni-prediction).

FIG. 10 illustrates examples of spatial neighbors used in derivingspatial merge candidates in the HEVC merge process.

FIG. 11 illustrates examples of samples involved in deblocking filter(DBF) on/off decision, filter selection, and filtering.

FIG. 12 illustrates examples of gradient patterns used in sampleadaptive offset (SAO); (a) horizontal; (b) vertical; (c) diagonal; and(d) 45° diagonal gradient patterns.

FIG. 13 illustrates example locations of the samples used for derivationof α and β in cross-component linear model prediction.

FIG. 14 illustrates an example overlapped block motion compensation.

FIG. 15 illustrates an example associated with local illuminationcompensation.

FIG. 16 illustrates examples of adaptive loop filter (ALF) shapes: (a)5×5 diamond; (b) 7×7 diamond; and (c) 9×9 diamond filter shapes.

FIG. 17 illustrates an example with target, template, and referencesample in decoder-side intra mode derivation (DIMD).

FIG. 18 illustrates example CMP: (a) 3D representation; and (b) 3×2frame-packing configuration.

FIG. 19 illustrates example availability of spatial neighbors when aface discontinuity is located: (a) above; (b) below; (c) on the left; or(d) on the right of the current block.

FIG. 20 illustrates example availability of reconstructed samples when aface discontinuity is located: (a) above; (b) below; (c) on the left; or(d) on the right of the current block.

FIG. 21 illustrates an example comparison of: (a) sub-block based motioncompensation, (b) sub-block based motion compensation with sub-blockmerging, and (c) sub-block based motion compensation with sub-blockmerging near face discontinuities.

FIG. 22 illustrates an example comparison of: (a) motion compensation,and (b) motion compensation near face discontinuities.

FIG. 23 illustrates example availability of the reconstructed samplesused for cross-component linear model prediction when a facediscontinuity is located: (a) above; or (b) on the left of the currentblock.

FIG. 24 illustrates an example comparison of an external overlappedblock motion compensation (OBMC)-based motion compensation based on: (a)an OBMC design, (b) a row/column based sub-block merging, and (c)sub-block merging near face discontinuities.

FIG. 25A is a system diagram illustrating an example communicationssystem in which one or more disclosed embodiments may be implemented.

FIG. 25B is a system diagram illustrating an example wirelesstransmit/receive unit (WTRU) that may be used within the communicationssystem illustrated in FIG. 25A according to an embodiment.

FIG. 25C is a system diagram illustrating an example radio accessnetwork (RAN) and an example core network (CN) that may be used withinthe communications system illustrated in FIG. 25A according to anembodiment.

FIG. 25D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 25A according to an embodiment.

DETAILED DESCRIPTION

A detailed description of illustrative embodiments will now be describedwith reference to the various Figures. Although this descriptionprovides a detailed example of possible implementations, it should benoted that the details are intended to be exemplary and in no way limitthe scope of the application.

VR systems may use one or more omnidirectional videos. For example, oneor more omnidirectional videos may include one or more 360-degreevideos. The 360-degree videos may be viewed from 360-degree angles inthe horizontal direction and from 180-degree angles in the verticaldirection. VR systems and 360-degree videos may be used for mediaconsumption beyond Ultra High Definition (UHD) services. Free view TV(FTV) may test the performance of solutions. For example, FTV may testthe performance of a 360-degree video (e.g., or an omnidirectionalvideo) based system and/or a multi-view based system.

VR systems may include a processing chain. The processing chain mayinclude capturing, processing, display, and/or applications. Withrespect to capturing, a VR system may use one or more cameras to capturescenes from different divergent views (e.g., 6 to 12 views). The viewsmay be stitched together to form a 360-degree video (e.g., in highresolution such as 4K or 8K). The client and/or user side of a VR systemmay include a computation platform, a head mounted display (HMD), and/orone or more head tracking sensors. The computation platform may receiveand/or decode 360-degree videos. The computation platform may generate aviewport for display. Two pictures (e.g., one for each eye) may berendered for the viewport. The two pictures may be displayed in the HMDfor stereo viewing. One or more lenses may be used to magnify imagesdisplayed in the HMD (e.g., for better viewing). The head trackingsensors may keep track (e.g., constantly keep track) of the viewer'shead orientation. Orientation information may be fed to the VR system todisplay the viewport picture for that orientation. A VR system mayprovide a specialized touch device. For example, a specialized touchdevice may allow a viewer to interact with objects in the virtual world.A VR system may be driven by a workstation with a graphic processingunit (GPU) support. A VR system may use a mobile device (e.g., asmartphone) as a computation platform, as a HMD display and/or as a headtracking sensor. Spatial resolution of an HMD may be, for example,2160×1200. A refresh rate may be, for example, 90 Hz. A field of view(FOV) may be, for example, about 110 degrees. Sampling rate fora headtracking sensor may be, for example, 1000 Hz, to capture fast movements.A VR system may comprise lens and a cardboard, and may be driven by asmartphone. A VR system may be used for gaming. One or more 360-degreevideo streaming services may be provided.

A VR system may be capable of providing interactivity and/or hapticfeedback. A HMD that is big may not be convenient for a person to wear.A resolution of 2160×1200 for stereoscopic views (e.g., as provided bycertain HMDs) may not be sufficient, and may cause dizziness anddiscomfort for some users. Resolution increase may be desirable VRexperience may be enhanced by combining the visual effects of a VRsystem with force feedback of the real world. A VR roller coasterapplication may be an example of combining the visual effects of a VRsystem with force feedback of the real world.

360-degree videos may be compressed and/or delivered, for example, usingDynamic Adaptive Streaming over HTTP (DASH)-based video streamingtechniques. 360-degree video content may be represented with a spheregeometry structure. For example, synchronized multiple views may becaptured by multiple cameras and may be stitched on a sphere. Thesynchronized multiple views may be stitched on the sphere as an (e.g.,one) integral structure. The sphere information may be projected onto a2D planar surface via a geometry conversion process. For example, thesphere information may be projected onto a 2D planar surface using anequirectangular projection (ERP). FIG. 1(a) shows an example spheresampling in longitudes (φ) and latitudes (θ). FIG. 1(b) shows an examplesphere being projected onto a 2D plane using ERP. The longitude φ in therange [−π, π] may be referred to as yaw, and the latitude θ in the range[−π/2, π/2] may be referred to as pitch (e.g., in aviation). π may bethe ratio of a circle's circumference to its diameter. (x, y, z) mayrepresent a point's coordinates in a 3D space. (ue, ve) may represent apoint's coordinates in a 2D plane after ERP. ERP may be representedmathematically, for example, as shown in Equations (1) and/or (2).

ue=(φ/(2/π)+0.5)*W  (1)

ve=(0.5−θ/π)*H  (2)

where W and H may be the width and height, respectively, of a 2D planarpicture. As shown in FIG. 1(a), the point P may be a cross point betweenlongitude L4 and latitude A1 on the sphere. P may be mapped to a uniquepoint q in FIG. 1(b) in the 2D plane using Equations (1) and/or (2).Point q in the 2D plane shown in FIG. 1(b) may be projected back topoint P on the sphere shown in FIG. 1(a), for example via inverseprojection. The field of view (FOV) in FIG. 1(b) shows an example of anFOV in a sphere being mapped to 2D plane with a viewing angle along theX axis at about 110 degrees.

One or more 360-degree videos may be mapped to 2D videos. For example,360-degree videos may be mapped to 2D videos using ERP. The 360-degreevideos may be encoded with a video codec such as H.264 or highefficiency video coding (HEVC), and may be delivered to a client. Forexample, the 360-degree videos may be mapped to 2D video, and the 2Dvideo may be encoded and delivered to the client. At the client side,the videos may be decoded (e.g., in equirectangular format) and renderedbased on the user's viewport, for example by projecting and displayingthe portion belonging to an FOV in the equirectangular pictures onto anHMD. The characteristics of an equirectangular 2D picture may bedifferent from a non-equirectangular 2D picture (e.g., a rectilinearvideo picture). FIG. 1(c) shows an example equirectangular picture. Thetop portion of the picture shown in FIG. 1(c) may correspond to theNorth Pole, and the bottom portion may correspond to the South Pole. Asshown in FIG. 1(c), the top and/or the bottom portions may be stretched.For example, the top and/or the bottom portions may be stretchedcompared to the middle portion of the picture corresponding to theEquator. The stretching in the top and/or bottom portions may indicatethat equirectangular sampling in the 2D spatial domain is uneven.

As shown in FIG. 1 (c), the top and bottom portions of the ERP picture,which may correspond to North Pole and South Pole respectively, may bestretched compared to the middle portion of the picture. The sphericalsampling density may be uneven for ERP format. Various geometricprojection formats may be used to map 360-degree video onto multiplefaces. FIG. 2 (a) shows an example of cubemap projection (CMP) geometry.The CMP may include 6 square faces, which may be labeled as PX, PY, PZ,NX, NY, NZ, where P may stand for positive, N may stand for negative,and X, Y, Z may refer to the axes. These faces may also be labeled usingnumbers 0-5, e.g. according to PX (0), NX (1), PY (2), NY (3), PZ (4),NZ (5). The lateral length of each face may be 2, e.g. if the radius ofthe tangent sphere is 1. The 6 faces of CMP format may be packedtogether into a single picture. Some faces may be rotated by a certaindegree, e.g., to maximize continuity between neighboring faces. FIG. 2(b) shows an example packing method to place 6 faces into a rectangularpicture, where (e.g., for better visualization) a face index (e.g., eachface index) is put in the direction that is aligned with thecorresponding rotation of the face. For example, faces #3 and #1 may berotated counter-clockwise by 270 and 180 degrees, respectively, whilethe other faces may not be rotated. An example picture with CMP is givenin FIG. 2 (c). As shown in FIG. 2 (c), the top row of 3 faces may bespatially neighboring faces in the 3D geometry and may have continuoustexture, and the bottom row of 3 faces may be spatially neighboringfaces in the 3D geometry and therefore may have continuous texture. Thetop face row and the bottom face row may not be spatially continuous in3D geometry, and a seam (e.g., a discontinuous boundary) may existbetween the two face rows. A face boundary between two or more adjoiningblocks that are not spherical neighbors may be referred to as a facediscontinuity.

In CMP, assuming the sampling density is equal to 1 at the center of aface (e.g., each face), the sampling density may increase towards theedges, which means that the texture around the edges may be stretchedcompared to that at the center. In different cubemap-based projections,e.g., equi-angular cubemap projection (EAC) and/or adjusted cubemapprojection (ACP), a face (e.g., each face) may be adjusted using anon-linear warping function in vertical and/or horizontal directions toachieve a more even sampling density. In EAC, the adjustment may beperformed using a tangent function, whereas the adjustment may beperformed using a second order polynomial function in ACP. Ageneralization of EAC and ACP, which may be called hybrid cubemapprojection (HCP), may be used. In HCP, the adjustment function and itsparameters may be tuned for a face (e.g., each face) and directionindividually to provide better coding efficiency. The cube-basedprojections may be packed in a similar fashion as for the CMP.

FIG. 3 illustrates an example work flow for 360-degree video processing.A 360-degree video capture may be captured using one or more cameras.For example, one or more cameras may be used to capture a 360-degreevideo covering a spherical space. The videos may be stitched together.For example, the videos may be stitched together using anequirectangular geometry structure. The equirectangular geometrystructure may be converted to another geometry structure, such as acubemap geometry, for encoding (e.g., encoding with video codecs). Thecoded video may be delivered to the client, for example, via dynamicstreaming and/or broadcasting. The video may be decoded, for example, atthe receiver. The decompressed frame may be unpacked to a display suchas a display geometry. For example, the display geometry may be in anequirectangular geometry. The geometry may be used for rendering. Forexample, the geometry may be used for rendering via viewport projectionaccording to a user's viewing angle.

FIG. 4 shows a block diagram of an example block-based hybrid videoencoding system 600. The input video signal 602 may be processed blockby block. Extended block sizes (e.g., referred to as a coding unit orCU) may be used (e.g., in HEVC) to compress high resolution (e.g., 1080pand/or beyond) video signals. A CU may have up to 64×64 pixels (e.g., inHEVC). A CU may be partitioned into prediction units or PUs, for whichseparate predictions may be applied. For an input video block (e.g., amacroblock (MB) or CU). spatial prediction 660 or temporal prediction662 may be performed. Spatial prediction (e.g., or intra prediction) mayuse pixels from already coded neighboring blocks in the same videopicture and/or slice to predict a current video block. Spatialprediction may reduce spatial redundancy inherent in the video signal.Temporal prediction (e.g., referred to as inter prediction or motioncompensated prediction) may use pixels from already coded video picturesto predict a current video block. Temporal prediction may reducetemporal redundancy inherent in the video signal. A temporal predictionsignal for a given video block may be signaled by a motion vector thatindicates the amount and/or direction of motion between the currentblock and its reference block. If multiple reference pictures aresupported (e.g., in H.264/AVC or HEVC), the reference picture index of avideo block may be signaled to a decoder. The reference index may beused to identify from which reference picture in a reference picturestore 664 the temporal prediction signal may come.

After spatial and/or temporal prediction, a mode decision 680 in theencoder may select a prediction mode, for example based on arate-distortion optimization. The prediction block may be subtractedfrom the current video block at 616. Prediction residuals may bede-correlated using a transform module 604 and a quantization module 606to achieve a target bit-rate. The quantized residual coefficients may beinverse quantized at 610 and inverse transformed at 612 to formreconstructed residuals. The reconstructed residuals may be added backto the prediction block at 626 to form a reconstructed video block. Anin-loop filter such as a de-blocking filter and/or an adaptive loopfilter may be applied to the reconstructed video block at 666 before itis put in the reference picture store 664. Reference pictures in thereference picture store 664 may be used to code future video blocks. Anoutput video bit-stream 620 may be formed. Coding mode (e.g., inter orintra), prediction mode information, motion information, and/orquantized residual coefficients may be sent to an entropy coding unit608 to be compressed and packed to form the bit-stream 620.

FIG. 5 shows a general block diagram of an example block-based videodecoder. A video bit-stream 202 may be received, unpacked, and/orentropy decoded at an entropy decoding unit 208. Coding mode and/orprediction information may be sent to a spatial prediction unit 260(e.g., if intra coded) and/or to a temporal prediction unit 262 (e.g.,if inter coded). A prediction block may be formed the spatial predictionunit 260 and/or temporal prediction unit 262. Residual transformcoefficients may be sent to an inverse quantization unit 210 and aninverse transform unit 212 to reconstruct a residual block. Theprediction block and residual block may be added at 226. Thereconstructed block may go through in-loop filtering 266 and may bestored in a reference picture store 264. Reconstructed videos in thereference picture store 264 may be used to drive a display device and/orto predict future video blocks.

Intra prediction and/or inter prediction may be performed in videocoding. Intra prediction may be used to predict the sample value withneighboring reconstructed samples. For example, the reference samplesused for intra prediction of a current transform unit (TU) are shown inFIG. 6. The reference samples may be from the left and/or topneighboring reconstructed samples as shown in the shaded boxes in FIG.6.

FIG. 7 illustrates an example indication of angular intra predictionmodes. HEVC may support a variety of (e.g., 35) intra prediction modes,such as a DC mode (e.g., mode 1), a planar mode (e.g., mode 0), and 33directional or angular intra prediction modes. The planar predictionmode may generate a first order approximation for a current block using,for example, the top and left reconstructed samples. The angularprediction modes may be designed (e.g., specially designed) to predictdirectional textures. The intra prediction mode may be selected (e.g.,at the encoder side). For example, the intra prediction mode may beselected at the encoder side by minimizing the distortion between aprediction generated by an intra prediction mode (e.g., each intraprediction mode) and one or more original samples. The intra predictionmode may be selected based on minimizing a rate distortion cost usingrate distortion optimization. The intra prediction mode may be encoded,for example, using most probable mode (MPM) for intra coding. MPM mayreuse the intra angular mode of spatial neighboring PUs. FIG. 8illustrates examples of spatial neighbors used for deriving the MPMs inthe HEVC intra angular process. FIG. 8 may show the spatial neighbors(e.g., bottom left, left, top right, top, and/or top left) used for MPMcandidate derivation in HEVC. A selected MPM candidate index may becoded. An MPM candidate list may be constructed at the decoder side(e.g., in the same way as at the encoder). An entry with the signaledMPM candidate index may be used as the intra angular mode of current PU.

FIG. 9 illustrates an example inter prediction with one motion vector(MV) (e.g., uni-prediction). The blocks B0′ and B1′ in the referencepicture of FIG. 9 may be the reference blocks of block B0 and B1,respectively. The motion vector information may be encoded, for example,by using motion vector prediction and/or merge mode for inter coding.The motion vector prediction may use the motion vectors from spatialneighboring PUs or a temporal collocated PU as the current MV'spredictor. The encoder and/or the decoder may form a motion vectorpredictor candidate list in the same manner. The index of the selectedMV predictor from the candidate list may be coded and/or signaled to thedecoder. The decoder may construct a MV predictor list, and the entrywith the signaled index may be used as the predictor of the current PU'sMV. The merge mode may reuse the MV information of spatial and/ortemporal neighboring. The encoder and/or the decoder may form a motionvector merge candidate list in the same manner. FIG. 10 illustratesexamples of spatial neighbors being used in deriving spatial mergecandidates in an HEVC merge process. As shown in FIG. 10, the spatialneighbors (e.g., bottom left, left, top right, top, and/or top left) maybe used for merge candidate derivation in HEVC. The selected mergecandidate index may be coded. The merge candidate list may beconstructed at the decoder side (e.g., in the same way as at in theencoder). The entry with the signaled merge candidate index may be usedas the MV of the current PU.

In HEVC, one or more (e.g., two) in-loop filters (e.g., a deblockingfilter (DBF) followed by a sample adaptive offset (SAO) filter), may beapplied to one or more reconstructed samples. The DBF may be configuredto reduce blocking artifacts due to block-based coding. DBF may beapplied (e.g., applied only) to samples located at PU and/or TUboundaries, except at the picture boundaries or when disabled at sliceand/or tiles boundaries. Horizontal filtering may be applied (e.g.,applied first) for vertical boundaries, and vertical filtering may beapplied for horizontal boundaries. FIG. 11 illustrates examples ofsamples involved in DBP on/off decision, filter selection, andfiltering. Given two adjacent blocks, P and Q, depending on the filterstrength, up to three sample columns (or rows) on each side of theboundary may be filtered in horizontal (or vertical) filtering, asdepicted in FIG. 11. SAO may be another in-loop filtering process thatmodifies decoded samples by conditionally adding an offset value to asample (e.g., each sample), based on values in look-up tablestransmitted by the encoder. SAO may have one or more (e.g., two)operation modes: band offset and edge offset modes. In the band offsetmode, an offset may be added to the sample value depending on the sampleamplitude. The full sample amplitude range may be divided into 32 bands,and sample values belonging to four of these bands may be modified byadding a positive or negative offset, which may be signaled for eachcoding tree unit (CTU). In the edge offset mode, the horizontal,vertical, and two diagonal gradients may be used for classification, asdepicted in FIG. 12. FIG. 12 illustrates examples of four gradientpatterns used in SAO. For each edge category, an offset may be signaledat CTU level.

Cross-component linear model prediction may be performed. RGB to YUVcolor conversion may be performed (e.g., to reduce the correlationbetween different channels). Cross-component linear model prediction maybe used to predict chroma samples from corresponding luma samples usinga linear model. The value of a given chroma sample p_(i,j) may bepredicted from the corresponding down sampled (e.g., if video is in 420or 422 chroma format) reconstructed luma sample values, L′_(i,j), asshown in Equation (3) (e.g., assuming a chroma block of N×N samples):

p _(i,j) =α·L _(i,j)′+β  (3)

The down sampled luma samples may be computed as shown in Equation (4):

$\begin{matrix}{L_{i,j}^{\prime} = \frac{\begin{matrix}{L_{{{2 \cdot i} - 2},{{2 \cdot j} - 1}} + {2 \cdot L_{{{2 \cdot i} - 1},{{2 \cdot j} - 1}}} +} \\{L_{{2 \cdot i},{{2 \cdot j} - 1}} + L_{{{2 \cdot i} - 2},{2 \cdot j}} + {2 \cdot L_{{{2 \cdot i} - 1},{2 \cdot j}}} + L_{{2 \cdot i},{2 \cdot j}}}\end{matrix}}{8}} & (4)\end{matrix}$

The parameters of the linear model may be derived by minimizing theregression error between the top and left neighboring reconstructedsamples and may be computed as shown in Equations (5) and (6):

$\begin{matrix}{\alpha = \frac{\begin{matrix}{{2 \cdot N \cdot \left\lbrack {{\Sigma_{i = 1}^{N}\left( {L_{i,0}^{\prime} \cdot C_{i,0}} \right)} + {\sum_{j = 1}^{N}\left( {L_{0,j}^{\prime} \cdot C_{0,j}} \right)}} \right\rbrack} -} \\\left. {\left( {{\sum_{i = 1}^{N}L_{i,0}^{\prime}} + {\sum_{j = 1}^{N}L_{0,j}^{\prime}}} \right) \cdot \left( {{\sum_{i = 1}^{N}C_{i,0}} + {\sum_{j = 1}^{N}C_{0,j}}} \right.} \right)\end{matrix}}{\begin{matrix}{{2 \cdot N \cdot \left\lbrack {{\Sigma_{i = 1}^{N}\left( {L_{i,0}^{\prime} \cdot L_{i,0}^{\prime}} \right)} + {\sum_{j = 1}^{N}\left( {L_{0,j}^{\prime} \cdot L_{0,j}^{\prime}} \right)}} \right\rbrack} -} \\{\left( {{\sum_{i = 1}^{N}L_{i,0}^{\prime}} + {\sum_{j = 1}^{N}L_{0,j}^{\prime}}} \right) \cdot \left( {{\sum_{i = 1}^{N}L_{i,0}^{\prime}} + {\sum_{j = 1}^{N}L_{0,j}^{\prime}}} \right)}\end{matrix}}} & (5)\end{matrix}$ $\begin{matrix}{\beta = \frac{\left( {{\Sigma_{i = 1}^{N}C_{i,0}} + {\Sigma_{j = 1}^{N}C_{0,j}}} \right) - {\alpha \cdot \left( {{\Sigma_{i = 1}^{N}L_{i,0}^{\prime}} + {\sum_{j = 1}^{N}L_{0,j}^{\prime}}} \right)}}{2 \cdot N}} & (6)\end{matrix}$

FIG. 13 illustrates example locations of samples used for derivation ofα and β in cross-component linear model prediction. For example, FIG. 13provides the location of the top and left neighboring reconstructedsamples used for the derivation of α and β. The neighboringreconstructed samples may be available at the encoder and/or thedecoder. The values of α and β may be derived at the encoder and/or thedecoder in the same way.

Overlapped block motion compensation may be performed.

Overlapped block motion compensation (OBMC) may be used to remove one ormore blocking artifacts at motion compensation stage. OBMC may beperformed for one or more (e.g., all) inter block boundaries except theright and bottom boundaries of one block. When a video block is coded ina sub-block mode (e.g., advanced temporal motion vector prediction(ATMVP) and/or spatial-temporal motion vector prediction (STMVP)), OBMCmay be performed for the sub-block's boundaries (e.g., each of thesub-block's boundaries). FIG. 14 illustrates an example concept of OBMC.When OBMC is applied to a sub-block (e.g., sub-block A in FIG. 14), inaddition to the motion vector of the current sub-block, motion vectorsof up to four neighboring sub-blocks may be used to derive theprediction signal of the current sub-block. The multiple predictionblocks using the motion vectors of neighboring sub-blocks may beaveraged to generate the final prediction signal of the currentsub-block.

Weighted average may be used in OBMC to generate the prediction signalof a block. The prediction signal using the motion vector of aneighboring sub-block may be denoted as PN, and the prediction signalusing the motion vector of the current sub-block may be denoted as PC.When OBMC is applied, the samples in the first/last four rows/columns ofPN may be weighted averaged with the samples at the same positions inPC. The samples to which the weighted averaging is applied may bedetermined, for example, according to the location of the correspondingneighboring sub-block. For example, when the neighboring sub-block is anabove neighbor (e.g., sub-block b in FIG. 14), the samples in the firstfour rows of the current sub-block may be adjusted. When the neighboringsub-block is a below neighbor (e.g., sub-block d in FIG. 14), thesamples in the last four rows of the current sub-block may be adjusted.When the neighboring sub-block is a left neighbor (e.g., sub-block a inFIG. 14), the samples in the first four columns of the current block maybe adjusted. When the neighboring sub-block is a right neighbor (e.g.,sub-block c in FIG. 14), the samples in the last four columns of thecurrent sub-block may be adjusted. When the current block is not codedin a sub-block mode, one or more weighting factors (e.g., {¼, ⅛, 1/16,1/32}) may be used for the first four rows/columns of PN, and one ormore weighting factors (e.g., {¾, ⅞, 15/16, 31/32}) may be used for thefirst four rows/columns of PC. When the current block is coded insub-block mode, the first two rows/columns of PN and PC may be averaged.In this case, one or more weighting factors (e.g., {¼, ⅛}) may be usedfor PN, and one or more weighting factors (e.g., {¾, ⅞}) may be used forPC.

Local illumination compensation may be performed.

Illumination compensation (IC) may be based on a linear model forillumination changes, using, for example, a scaling factor a and/or anoffset b. IC may be enabled/disabled adaptively for an inter coded block(e.g., each inter coded block). FIG. 15 illustrates an example of IC. Asillustrated in FIG. 15, when IC is applied for a block, a least meansquare error (LMSE) method may be employed (e.g., to derive theparameters a and b). For example, the parameters a and b may be derivedby minimizing distortion between neighboring samples of the currentblock (e.g., the template) and their corresponding reference samples inthe temporal reference picture. As illustrated in FIG. 15, the templatemay be subsampled (e.g., 2:1 subsampling), which may reduce complexity.As shown in FIG. 15, the shaded samples (e.g., only the shaded samples)may be used to derive a and b.

An adaptive loop filter (ALF) may be used. For the luma component, oneor more (e.g., up to three) diamond filter shapes may be selected: forexample, 5×5, 7×7, and 9×9, as depicted in FIG. 16 (a), (b), and (c),respectively. FIG. 16 illustrates example ALF filter shapes. Theselected filter may be signaled at the picture level. For the chromacomponents, the 5×5 diamond shape may be used (e.g., always used). Forthe luma component, a 2×2 block (e.g., each 2×2 block) may be classifiedinto one out of 25 categories to select appropriate filter coefficientsfor that block. No classification may be performed for the chromacomponents, e.g., one set of coefficients may be used for one or more(e.g., all) chroma samples. The classification may be performed byanalyzing the activity and directionality of the gradients in aneighborhood around each 2×2 block. The horizontal, vertical, and twodiagonal gradients may be computed using a 1-D Laplacian in aneighborhood of 6×6 samples. One or more (e.g., three) geometrictransformations of filter coefficients, e.g., diagonal, vertical flip,and/or rotation, may be applied for each 2×2 block (e.g., depending onthe block's gradient values). For the luma component, filtering may becontrolled at the CU level, for example by using a flag to signal if ALFis applied or not. For the chroma components, ALF may be enabled ordisabled for the whole picture.

Decoder-side intra mode derivation (DIMD) may be performed. DIMD mayderive information (e.g., at the encoder and/or the decoder) from theneighboring samples of a block (e.g., the neighboring reconstructedsamples of one block). FIG. 17 illustrates an example of deriving (e.g.,without signaling) intra mode using DIMD. As seen in FIG. 17, a targetmay denote a block as a current block (e.g., of block size N). An intramode of the current block may be estimated. The template (e.g., asindicated by the diagonally patterned region in FIG. 17) may indicate aset of samples (e.g., already reconstructed samples). The samples may beused to derive the intra mode. The template's size may be indicated bythe number of samples within the template that extends above and to theleft of the target block, e.g., L as seen in FIG. 17. A reference of thetemplate (e.g., as indicated by the dotted region in FIG. 17) may be aset of neighboring samples. The neighboring samples may be located aboveand to the left of the template. For intra prediction mode (e.g., eachintra prediction mode), DIMD may calculate the sum of absolutedifferences (SAD) between the reconstructed template samples and itsprediction samples. The prediction samples may be obtained from thereference samples of the template. The intra prediction mode that yieldsthe minimum SAD may be selected as the intra prediction mode of a block(e.g., the final intra prediction mode of the target block).

For geometries composed of different faces (e.g., CMP, octahedronprojection (OHP), icosahedral projection (ISP), and/or the like), one ormore discontinuities may appear between two or more adjacent faces in aframe-packed picture (e.g., regardless of the compact face arrangement).For example, FIG. 2(c) illustrates an example 3×2 CMP. In FIG. 2(c), the3 faces in the top half may be horizontally continuous in 3D geometry.The 3 faces in the bottom half may be horizontally continuous in 3Dgeometry. The top half and bottom half may be discontinuous in 3Dgeometry. For 360-degree video, because of discontinuities, aneighboring block in the frame-packed picture may not necessarily berelevant.

FIG. 18 illustrates an example of CMP. FIG. 18(a) illustrates an example3D representation of the CMP. FIG. 18(b) illustrates an example 3×2frame-packing configuration of the CMP. As shown in FIG. 18(a) and/or(b), block D may be the frame-packed neighbor located above block A. Aframe-packed neighbor may be or may include a block that neighbors thecurrent block in the frame-packed picture. A spherical neighbor may beor may include a block that neighbors the current block in 3D geometry.A frame-packed neighbor may also be a spherical neighbor. Consideringthe 3D geometry, block E may be the spherical neighbor located aboveblock A. If video codec(s) designed for 2D video is used, theframe-packed neighbor D may be used to predict the current block A, forexample, in the form of intra prediction, intra MPM, merge mode, motionvector prediction, and/or the like. Information from D may not beappropriate to predict A (e.g., due to the inherent discontinuitybetween D and A) and may degrade coding efficiency. A spherical neighbor(e.g., block E) may be used when deriving relevant coding information(e.g., intra mode, motion vector, reference samples, and/or the like) topredict the current block (e.g., block A).

The spherical neighbors may be derived. For example, the sphericalneighbors may be derived at the sample level (e.g., to derive referencesamples for intra prediction and/or for a cross-component linear model).2D to 3D geometry and/or 3D to 2D geometry conversions may be applied toderive the spherical neighbors. A look-up-table (LUT) may be used topre-store the locations of spherical neighbors.

CTUs in a current picture/slice/tile may be processed in raster scanorder. Information from a limited number of frame-packed neighboringblocks may be buffered (e.g., using a cache). When spherical neighborsare considered, the reference sample and/or coding information may befar from the current block in raster scan order. For example, block Efrom FIG. 18(b) may be farther from A in raster scan order than blocksB, C, and D. The information from block E may be removed from the cachebefore block A is coded.

A frame-packed neighbor block may be used to predict the current blockin 360-degree video coding when (e.g., only when) the frame-packedneighbor block is the spherical neighbor block of the current block. Forthe example depicted in FIG. 18(a)-(b), block B may be a frame-packedand spherical neighbor with respect to block A, whereas blocks C and Dmay be frame-packed neighbors to block A, but not spherical neighbors ofblock A. Inferring information across face discontinuities may bedisabled.

The left (L), above (A), above right (AR), above left (AL), and belowleft (BL) neighbors may be used to infer information (e.g., because ofraster scan processing) in 2D video coding (e.g., see FIG. 8 and FIG.10). If the current block is located on the right side of a facediscontinuity, the left, above left, and/or below left frame-packedneighbor blocks may be located on the other side of the facediscontinuity and may be considered as unavailable for inferringattributes, e.g., for deriving the list of most probable modes in intraprediction, for deriving motion vector candidates in motion vectorprediction and/or merge mode, OBMC, and/or the like. Similarconsiderations may be applied to a current block which may be located onthe left side of, above, and/or below a face discontinuity. In this way,non-relevant spatial candidates may be excluded when inferringattributes from neighboring blocks.

Reconstructed samples located above and/or on the left of the currentblock may be used in 2D video coding (e.g., because of raster scanprocessing) for predicting the current block (e.g., see FIG. 6 and FIG.13). If the current block is located on the right side of a facediscontinuity, the reconstructed samples located on the left side of theblock, e.g., R_(0,0) . . . R_(0,2N) (e.g., see FIG. 6 and FIG. 13), maybe located on the other side of the face discontinuity and may notcorrelate with the current block samples. In this case, thereconstructed samples may be considered as unavailable in one or moreprediction approaches, e.g., DC, planar, and/or angular modes in intraprediction, cross-component linear model prediction, OBMC, and/orin-loop filtering. In this way, poorly correlated reconstructed samplesmay be excluded when predicting and/or filtering the current block usingneighboring reconstructed samples.

Reconstructed samples and/or coding information from spatial neighborsacross face discontinuities may be discounted.

The techniques described herein may be applied to a face discontinuityand/or a face continuity, e.g., a boundary between two faces in theframe-packed picture that are also neighboring faces in 3D geometry.

Face discontinuities in a frame-packed picture may be determined. Inexamples, frame-packing information may be signaled in the bit stream toidentify one or more faces (e.g., each face) in the frame-packedpicture. For one or more (e.g., every) pair of neighboring faces in theframe-packed picture, the shared edge may be defined as continuous ifthe two faces share the same edge in 3D geometry. If the two faces donot share the same edge in 3D geometry, this edge may be defined asdiscontinuous.

For example, a frame-packed picture may contain M×N faces (e.g., in FIG.2 (b), M=3 and N=2), (M−1)×N vertical edges may exist between faces inthe picture, and M×(N−1) horizontal edges may exist between faces in thepicture. A total of (M−1)×N+M×(N−1) flags may be signaled, for exampleto specify whether an edge is continuous or not, as shown in Table 1.The edges may be scanned in a specific order, e.g., from top to bottomand from left to right. Table 1 may illustrate this set of syntaxelements being placed in Video Parameter Set. Other sequence levelparameter sets, such as Picture Parameter Set (PPS) or SequenceParameter Set (SPS) may be used to carry this information.

TABLE 1 Video parameter set RBSP Descriptor video_parameter_set_rbsp( ){  ...  face_discontinuity_param_present_flag u(1)  if(face_discontinuity_param_present_flag ) {   num_face_rows ue(v)  num_face_columns ue(v)   for( i = 0; i <(num_face_rows−1)*num_face_columns + num_face_rows*(num_face_columns−1);i++ ) {    face_discontinuity_flag[ i ] u(1)   }  }  ... }

In Table 1, the parameter face_discontinuity_param_present_flag mayspecify whether one or more of the syntax elements num_face_rows,num_face_columns, and face_discontinuity_flag[i] are present. When theparameter face_discontinuity_param_present_flag is not present in thebitstream, the value of the parameter may be inferred to be a value thatindicates that the face discontinuity parameters are absent (e.g., 0).

The parameter num_face_rows may specify the number of face rows in theframe-packed picture. When the parameter num_face_rows is not present inthe bitstream, the value of the parameter may be set to a default value(e.g., 1).

The parameter num_face_columns may specify the number of face columns inthe frame-packed picture. When the parameter num_face_columns is notpresent in the bitstream, the value of the parameter may be set to adefault value (e.g., 1).

Parameters num_face_rows_minus1 and/or num_face_columns_minus1 may besignaled (e.g., instead of and/or in addition to signaling num_face_rowsand num_face_columns) to reduce the number of bits to code the syntaxelements.

Parameter face_discontinuity_flag[i] may specify whether the i-th faceedge is discontinuous or not.

In examples, coordinates of the two endpoints of one or more facediscontinuities (e.g., each face discontinuity) in the frame-packedpicture may be signaled (e.g., signaled explicitly). Endpoints forhorizontal and/or vertical discontinuities may be signaled. Endpointsfor diagonal discontinuities may be signaled. Diagonal discontinuitiesmay be used, for example, for triangular based geometries (e.g., OHPand/or ISP). Table 2 illustrates example syntax elements at the videolevel.

TABLE 2 Video parameter set RBSP Descriptor video_parameter_set_rbsp( ){  ...  face_discontinuity_param_present_flag u(1)  if(face_discontinuity_param_present_flag ) {   num_face_discontinuitiesue(v)   for( i = 0; i < num_face_discontinuities; i++ ) {   face_discontinuity_start_point_x[ i ] ue(v)   face_discontinuity_start_point_y[ i ] ue(v)   face_discontinuity_end_point_x[ i ] ue(v)   face_discontinuity_end_point_y[ i ] ue(v)   }  }  ... }

In Table 2, the parameter face_discontinuity_param_present_flag mayspecify whether one or more of the syntax elementsnum_face_discontinuities, face_discontinuity_start_point_x,face_discontinuity_start_point_y, face_discontinuity_end_point_x, and/orface_discontinuity_end_point_y are present. When the parameterface_discontinuity_param_present_flag is not present in the bitstream,the value of the parameter may be inferred to be a value that indicatesthat the face discontinuity parameters are absent (e.g., 0).

The parameter num_face_discontinuities may specify the number of facediscontinuities in the frame-packed picture. When the parameternum_face_discontinuities is not present in the bitstream, the value ofthe parameter may be be set to a default value (e.g., 1). A parameternum_face_discontinuities_minus1 may be signaled (e.g., instead of and/orin addition to signaling num_face_discontinuities). The value of theparameter num_face_discontinuities_minus1 may be the number of facediscontinuities in the frame-packed picture minus one.

The parameter face_discontinuity_start_point_x[i] may specify the xcoordinate in the frame-packed picture of the start point of the i-thface discontinuity. The value of the parameterface_discontinuity_start_point_x[i] may be in the range of 0 topicture_width-1 (e.g., inclusively).

The parameter face_discontinuity_start_point_y[i] may specify the ycoordinate in the frame-packed picture of the start point of the i-thface discontinuity. The value of the parameterface_discontinuity_start_point_x[i] may be in the range of 0 topicture_height-1 (e.g., inclusively).

The parameter face_discontinuity_end_point_x[i] may specify the xcoordinate in the frame-packed picture of the end point of the i-th facediscontinuity. The value of the parameterface_discontinuity_start_point_x[i] may be in the range of 0 topicture_width-1 (e.g., inclusively).

The parameter face_discontinuity_end_point_y[i] may specify the ycoordinate in the frame-packed picture of the end point of the i-th facediscontinuity. The value of the parameterface_discontinuity_start_point_x[i] may be in the range of 0 topicture_height-1 (e.g., inclusively).

One or more of the parameters defined at the video level may be signaled(e.g., signaled instead of and/or in addition) at the sequence and/orpicture level, for example if the projection geometry and/orframe-packing is changed during the video encoding. Fixed length codingof the syntax elements may be used (e.g., instead of ue(v)). The bitlength of the syntax elements may be determined by ceil(log2(picture_width)) or ceil(log 2(picture_height)).

If one or more exemplary approaches described herein are used, a list offace discontinuities may be generated. For example, K vertical facediscontinuities and L horizontal face discontinuities may be identified.A list of (K+L) face discontinuities may be split into two lists: a listof K vertical face discontinuities, which may be denoted as D_(v), and alist of L horizontal face discontinuities, which may be denoted asD_(h). For a face discontinuity d, its two endpoints in the frame-packedpicture, which may be denoted as A_(d) and B_(d) may be determined. Ablock may be identified by its upper left coordinate, which may bedenoted as C, its width, which may be denoted as W, and its height,which may be denoted as H. To check if a horizontal discontinuity islocated above the block, a horizontal face discontinuity check may beperformed as shown in Table 3.

TABLE 3 An example approach to check discontinuity discontinuity = falseforeach d ∈ D_(h) do  if A_(d,y) = C_(y) and min(A_(dx), B_(d,x) ) ≤C_(x) + W and max(A_(dx), B_(d,x) ) ≥ C_(x) then   discontinuity = true  break end

A similar approach may be used to determine if a discontinuity islocated below, on the left side of, and/or on the right side of a block.A similar approach may be used to determine if a discontinuity islocated near a particular sample position.

A frame-packing arrangement may be determined at a high level (e.g., asequence level or picture level). Face discontinuities may be determinedat the high level and may remain the same through multiple pictures. Anarray may be pre-calculated at a given granularity to store whether adiscontinuity exists for a block. For example, if the array is definedat the block level, a face discontinuity flag may be calculated for eachblock and may be stored in the array. The block may be of apre-determined size, for example 4×4. Whether a discontinuity existsduring encoding/decoding for the current block may be determined.

FIG. 2(b) illustrates an example 3×2 cubemap frame-packing. In FIG.2(c), a horizontal discontinuity may occur in the middle of the picture,and there may be no vertical discontinuities. Blocks that adjoin thediscontinuity line and/or samples that lie on top of the discontinuityline may have the discontinuity flag set to true. One or more otherblocks (e.g., all other blocks) and/or samples may have thediscontinuity flag set to false.

The positions of face boundaries (e.g., the positions of all the faceboundaries inside a frame-packed picture) may be signaled. The positionsof discontinuous face boundaries inside a frame-packed picture may besignaled (e.g., may only be signaled). A flag may be signaled for a faceboundary (e.g., each face boundary). The flag may indicate whether theface boundary is continuous or discontinuous.

Spatial candidates at face discontinuities may be identified.

Information may be inferred from neighboring blocks, e.g., for mostprobable mode in intra prediction, spatial-temporal motion vectorprediction (STMVP), OBMC, and/or merge mode in inter prediction. Theneighboring blocks may be spatial neighboring blocks or temporalneighboring blocks. Whether a current block is located at a facediscontinuity may be determined, e.g. based on the location of thecurrent block. A coding availability of a neighboring block may bedetermined, e.g., based on whether the neighboring block is on the sameside of the face discontinuity as the current block. Frame-packedneighbors that are not spherical neighbors of a current block (e.g.,neighboring blocks that are not on the same side of the facediscontinuity as the current block) may be considered unavailable fordecoding the current block. Frame-packed neighbors that are sphericalneighbors of the current block (e.g., neighboring blocks that are on thesame side of the face discontinuity as the current block) may beconsidered available for decoding the current block.

A decoding function may be performed on the current block, for examplebased on the coding availability of the neighboring block. The decodingfunction may include deriving a merge mode for the current block. Forexample, if the neighboring block is determined to be available, theneighboring block may be added to a merge candidate list (e.g., a listof candidate blocks). The neighboring block may be excluded from themerge candidate list if the neighboring block is determined to beunavailable.

FIG. 19 illustrates examples availability of spatial neighbors when aface discontinuity is located above (e.g., FIG. 19(a)), below (e.g.,FIG. 19(b)), on the left of (e.g., FIG. 19(c)), and/or on the right of(e.g., FIG. 19(d)) a current block. Blocks depicted in FIGS. 19(a)-(d)using a hatched pattern may be located on the other side of the facediscontinuity and may be considered unavailable (e.g., determined to beunavailable for decoding the current block). For example, if a facediscontinuity is located above the current block, the above left, above,and/or above right neighboring blocks may be considered unavailable, asdepicted in FIG. 19(a). If a face discontinuity is located below thecurrent block, the below left neighboring block may be consideredunavailable, as depicted in FIG. 19(b). If a face discontinuity islocated on the left side of the current block, the above left, left,and/or below left neighboring blocks may be considered unavailable, asdepicted in FIG. 19(c). If a face discontinuity is located on the rightside of the current block, the above right neighboring block may beconsidered unavailable, as depicted in FIG. 19(d).

Whether reconstructed samples at face discontinuities may be used forpredicting the current block may be determined, e.g. based on thelocation of the current block. Whether a current block is located at aface discontinuity may be determined. A coding availability of areconstructed sample may be determined, e.g., based on whether thereconstructed sample is on the same side of the face discontinuity asthe current block. One or more reconstructed samples that are located onthe other side of the face discontinuity that the current block adjoinsmay be considered unavailable (e.g., unavailable for decoding thecurrent block). One or more reconstructed samples that are located onthe same side of the face discontinuity that the current block adjoinsmay be considered available (e.g., available for decoding the currentblock). Reconstructed samples considered unavailable may be padded usingavailable reconstructed samples. For example, a reconstructed sampleconsidered unavailable may be replaced with one or more availablereconstructed samples.

FIG. 20 illustrates examples availability of reconstructed samples whena face discontinuity is located above (e.g., FIG. 20(a)), below (e.g.,FIG. 20(b)), on the left of (e.g., FIG. 20(c)), and/or on the right of(e.g., FIG. 20(d)) a current block. The reconstructed samples depictedin FIGS. 20(a)-(d) using a hatched pattern may be located on the otherside of the face discontinuity and may be considered unavailable (e.g.,determined to be unavailable for decoding the current block). Forexample, if a face discontinuity is located above the current block, thereconstructed samples located above the current block (e.g., R_(0,0) . .. R_(2N,0)) may be considered unavailable, as depicted in FIG. 20(a). Ifa face discontinuity is located below the current block, thereconstructed samples located below the current block (e.g., R_(0,N+1) .. . R_(0,2N)) may be considered unavailable, as depicted in FIG. 20(b).If a face discontinuity is located on the left side of the currentblock, the reconstructed samples located on the left side of the currentblock (e.g., R_(0,0) . . . R_(0,2N)) may be considered unavailable, asdepicted in FIG. 20(c). If a face discontinuity is located on the rightside of the current block, the reconstructed samples located on theright side of the current block (e.g., R_(N+1,0) . . . R_(2N,0)) may beconsidered unavailable, as depicted in FIG. 20(d).

More than one reference sample line may be used in one or more casesdescribed herein, and the same approach may be applied for rectangularblocks.

Certain implementation (e.g., cross-component linear model prediction,IC, etc.) may be disabled (e.g., completely disabled) if thereconstructed samples (e.g., all the reconstructed samples) used do notbelong to the same face. For example, if a face discontinuity crosses acurrent block and/or one or more samples of the current block belong toa different face from that of the template, IC may be disabled (e.g.,completely disabled). Disabling IC may avoid scaling and/or offsetting ablock using reconstructed samples that are located in different faces.

Motion compensation may be performed at face discontinuities. Interprediction modes (e.g., FRUC, alternative temporal motion vectorprediction (ATMVP), spatial-temporal motion vector prediction (STMVP),and/or affine motion compensated prediction) may employ sub-block basedmotion vector prediction. For example, if a group of sub-blocks have thesame motion information, motion compensation may be applied (e.g.,directly) to the group of sub-blocks (e.g., the entire group ofsub-blocks). If one or more sub-blocks are merged into a largersub-block-group (e.g., as a motion compensation unit), sub-blocks thatbelong to the same face may be merged together.

Motion compensation may be applied separately (e.g., on each side of aface discontinuity) and/or jointly. As illustrated in FIGS. 21 (a)-(c),if a coding block is crossed by a face discontinuity and one or moresub-blocks (e.g., all sub-blocks) on one side of the block have the samemotion information, motion compensation may be applied separately (e.g.,corresponding to MC0 and MC1 in FIG. 21 (c)). For example, motioncompensation may be applied separately to one or more groups on eachside of the face discontinuity. As illustrated in FIGS. 21 (a)-(c), if acoding block is not crossed by a face discontinuity, and one or moresub-blocks (e.g., all sub-blocks) on one side of the block have the samemotion information, motion compensation may be applied jointly (e.g.,corresponding to MC0 in FIG. 21 (b)). For example, motion compensationmay be applied jointly for each side of the coding block.

Motion compensation may be applied considering the face to which themerged sub-blocks belong. For example, if geometry padding is used,motion compensation may be applied using a corresponding padded face.Motion compensation using the corresponding padded face may derive oneor more reference samples for interpolation.

If a face discontinuity crosses a block/sub-block and thatblock/sub-block has one motion vector, motion compensation may be splitinto two or more motion compensation processes. For example, when facebased geometry padding is applied, motion compensation may be performedon a side (e.g., each side) of the face discontinuity. This techniquemay be similar to the concepts used for coding units and/or predictionunits. For example, whether a face discontinuity crosses the currentcoding unit (e.g., current block) may be determined. The current codingunit may be split into one or more prediction units (e.g., one on eachside of the face discontinuity). The prediction units may be used toperform motion compensated prediction. For example, motion compensationmay be performed for each prediction unit separately. As illustrated inFIGS. 22 (a) and (b), if a coding unit is crossed by a facediscontinuity, motion compensation may be applied separately (e.g.,corresponding to MC0 and MC1, in FIG. 22 (b)). For example, motioncompensation may be applied separately to a prediction unit on each sideof the face discontinuity. As illustrated in FIGS. 22 (a) and (b), if acoding unit is not crossed by a vertical and/or horizontal facediscontinuity, motion compensation may be applied jointly (e.g.,corresponding to MC0 in FIG. 22 (a)). For example, motion compensationmay be applied jointly for each side of the prediction unit.

Partitioning may be applied based on a face discontinuity. For example,the partitioning may be implicit and/or explicit. The partitioning mayalign a block boundary with a face discontinuity, which may avoid theblock being crossed by a face discontinuity.

Cross-component linear model prediction (CCLMP) at face discontinuitiesmay be performed. Whether to enable or disable CCLMP may be determinedfor a block based on, for example, the location of the block Forcross-component linear model prediction, the correlation betweenreconstructed and current block samples may be improved. For example,one or more reconstructed samples may be used for estimating parametersof a linear model. Reconstructed samples that are located on the otherside of a face discontinuity which a current block adjoins may bediscarded.

FIG. 23 illustrates examples availability of reconstructed samples usedfor cross-component linear model prediction when a face discontinuity islocated above (e.g., FIG. 23 (a)) or on the left of (e.g., FIG. 23 (b))the current block. Reconstructed samples depicted using a hatchedpattern may be located on the other side of the face discontinuity andmay be considered unavailable (e.g., determined to be unavailable fordecoding the current block). For example, if a face discontinuity islocated above the current block, the reconstructed samples located abovethe current block may be discarded (e.g., not used to predict theparameters of the linear model), as depicted in FIG. 23(a). In thiscase, the linear model parameters may be computed as shown in Equations(7) and (8):

$\begin{matrix}{\alpha = \frac{{N \cdot {\Sigma_{j = 1}^{N}\left( {L_{0,j}^{\prime} \cdot C_{0,j}} \right)}} - {\Sigma_{j = 1}^{N}{L_{0,j}^{\prime} \cdot \Sigma_{j = 1}^{N}}C_{0,j}}}{{N \cdot {\Sigma_{j = 1}^{N}\left( {L_{0,j}^{\prime} \cdot L_{0,j}^{\prime}} \right)}} - {\Sigma_{j = 1}^{N}{L_{0,j}^{\prime} \cdot \Sigma_{j = 1}^{N}}L_{0,j}^{\prime}}}} & (7)\end{matrix}$ $\begin{matrix}{\beta = \frac{{\Sigma_{j = 1}^{N}C_{0,j}} - {{\alpha \cdot \Sigma_{j = 1}^{N}}L_{0,j}^{\prime}}}{N}} & (8)\end{matrix}$

If a face discontinuity is located on the left side of the currentblock, the reconstructed samples located on the left side of the currentblock may be discarded (e.g., not used to predict the parameters of thelinear model), as depicted in FIG. 23(b). In this case, the linear modelparameters may be computed as shown in Equations (9) and (10):

$\begin{matrix}{\alpha = \frac{{N \cdot {\Sigma_{i = 1}^{N}\left( {L_{i,0}^{\prime} \cdot C_{i,0}} \right)}} - {\Sigma_{i = 1}^{N}{L_{i,0}^{\prime} \cdot \Sigma_{i = 1}^{N}}C_{i,0}}}{{N \cdot {\Sigma_{i = 1}^{N}\left( {L_{i,0}^{\prime} \cdot L_{i,0}^{\prime}} \right)}} - {\Sigma_{i = 1}^{N}{L_{i,0}^{\prime} \cdot \Sigma_{i = 1}^{N}}L_{i,0}^{\prime}}}} & (9)\end{matrix}$ $\begin{matrix}{\beta = \frac{{\Sigma_{i = 1}^{N}C_{i,0}} - {{\alpha \cdot \Sigma_{i = 1}^{N}}L_{i,0}^{\prime}}}{N}} & (10)\end{matrix}$

If a face discontinuity is located above and/or on the left side of thecurrent block, the reconstructed samples located above and/or on theleft side of the current block may be located on the other side of theface discontinuity, and cross-component linear model prediction may bedisabled for that block.

The same principle as described herein may be applied for rectangularblocks (e.g., without having to subsample the longer boundary to havethe same number of samples as the shorter boundary). Cross-componentlinear model prediction described herein may be used to predict betweentwo chroma components (e.g., in the sample domain or in the residualdomain). One or more cross-component linear models may be used, where across-component linear model prediction may be defined for a specificrange of sample values and applied as described herein.

Reconstructed samples located on the other side of the facediscontinuity which the current block adjoins may be consideredunavailable (e.g., instead of being discarded) and may be padded usingone or more available reconstructed samples.

Decoder-side intra mode derivation (DIMD) may be performed at facediscontinuities. A template may be discarded (e.g., marked asunavailable) in a DIMD search if part or all of the samples (e.g.,reconstructed samples) from the template and/or part or all of thereference samples used to predict the template are located on the otherside of the face discontinuity that the current block adjoins (e.g., thesamples are unavailable for decoding the current block).

For example, if a face discontinuity is located above a current block,one or more of the reconstructed samples from a top template and/or oneor more of the reference samples located above the top template may belocated on the other side of the face discontinuity that the currentblock adjoins. The top template may be discarded in a DIMD search.

For example, if a face discontinuity is located on the left side of acurrent block, then one or more of the reconstructed samples from a lefttemplate and/or one or more of the reference samples located on the leftside of the left template may be located on the other side of the facediscontinuity that the current block adjoins. The left template may bediscarded in a DIMD search.

Reconstructed samples that may be used to predict a template and whichmay be located on the other side of a face discontinuity that a currentblock adjoins may be) considered unavailable. This indication may beapplied to templates and/or to the reference samples, which may be usedto predict the templates. Reconstructed samples considered unavailablemay be padded (e.g., padded using available reconstructed samples).

The reconstructed samples may be located on the other side of the facediscontinuity that the current block adjoins. One or more sphericalneighbors may be used instead of frame-packed neighbors. The sphericalneighbors may be derived by unfolding the geometry and using the samplesfrom adjacent faces. This may be referred to as face-based padding. Forexample, as shown in FIGS. 18A and 18B, the top template of block A maybe derived from its spherical neighbor block E. Block D may not be usedfor padding if, for example, a face discontinuity exists between block Aand block D.

DIMD may be disabled for a block based on the block's location relativeto a face discontinuity. For example, DIMD may be disabled for one ormore of the following: blocks whose samples in the top and lefttemplates are not located in the same face to which the current blockbelongs, and/or blocks whose reference samples used to predict the topand left templates are not located in the same face to which the currentblock belongs.

Overlapped block motion compensation at face discontinuities may beperformed. To avoid adjustment using inappropriate samples in OBMC,adjustment based on neighboring blocks (or sub-blocks) that are locatedon the other side of the face discontinuity which the current block (orsub-block) adjoins may be skipped. If a face discontinuity is locatedabove the current block (or sub-block), the adjustment of the first rowsof the current block (or sub-block) using the motion vector of the aboveblock (or sub-block), which is located on the other side of the facediscontinuity, may be skipped. If a face discontinuity is located belowthe current block (or sub-block), the adjustment of the last rows of thecurrent block (or sub-block) using the motion vector of the below block(or sub-block), which is located on the other side of the facediscontinuity, may be skipped. If a face discontinuity is located on theleft side of the current block (or sub-block), the adjustment of thefirst columns of the current block (or sub-block) using the motionvector of the left block (or sub-block), which is located on the otherside of the face discontinuity, may be skipped. If a face discontinuityis located on the right side of the current block (or sub-block), theadjustment of the last columns of the current block (or sub-block) usingthe motion vector of the right block (or sub-block), which is located onthe other side of the face discontinuity, may be skipped.

An adjustment of a block or sub-block may be skipped based on a facediscontinuity crossing the block or sub-block. If, for example, a facediscontinuity crosses a current block or sub-block, the adjustment ofthe block or sub-block boundaries that are crossed by a facediscontinuity may be skipped. When a horizontal face discontinuitycrosses the current block or sub-block, the adjustment of the firstand/or last columns of the current block or sub-block may be skipped.When a vertical face discontinuity crosses the current block orsub-block, the adjustment of the first and/or last rows of the currentblock or sub-block may be skipped.

A boundary of a block or sub-block may be crossed by a facediscontinuity. If a boundary of the current block or sub-block iscrossed by a face discontinuity, OBMC may be applied. For example, OBMCmay be applied separately for a part (e.g., each part) of a blockboundary, which may be located on a side (e.g., each side) of the facediscontinuity, e.g. considering the corresponding neighboring MVslocated in the same face as a boundary segment (e.g., each boundarysegment).

Groups of sub-blocks may present similar (e.g., the same) motioninformation. OBMC may be applied (e.g., directly) to a group ofsub-blocks (e.g., an entire group of sub-blocks), for example, if thesub-blocks present the same motion information, as illustrated in FIGS.21(a)-(b).

Sub-blocks may be merged into one or more larger sub-block-groups basedon their locations relative to a face discontinuity. If one or moresub-blocks are merged into a larger sub-block-group, the sub-blocks(e.g., only the sub-blocks) that belong to the same face may be mergedtogether. For example, if a block is crossed by a horizontal facediscontinuity and the sub-blocks (e.g., all the sub-blocks) on the leftside of the block have the same motion information, the adjacentsub-blocks may be grouped together (e.g., into two groups). The adjacentsub-blocks that are grouped together may be used to perform externalOBMC-based motion compensations. As seen in FIG. 24(c), thesesub-block-groups may correspond to motion compensations (e.g., MC2 andMC3, in FIG. 24 (c)). As seen in FIG. 24(c), a group may be located on aside of a face discontinuity.

OBMC-based motion compensations may be applied considering the face towhich the sub-blocks belong. If, for example, geometry padding isperformed, the OBMC-based motion compensations may be applied using thecorresponding padded face. OBMC may be disabled for groups and/orsub-blocks based on their location relative to a face discontinuity. Forexample, OBMC may be disabled for groups and/or sub-blocks that belongto a different face than that of the current block's top-left position.In the example depicted in FIG. 24 (c), OBMC-based motion compensation(e.g., MC3 in FIG. 24 (c)) may be disabled.

OBMC may use the MVs of neighboring blocks or sub-blocks to performmotion compensation on the current block or sub-block. When aneighboring MV comes from a different face than the current block orsub-block, OBMC may be disabled for that MV. OBMC may combine one ormore prediction signals using the neighboring MVs to generate a finalprediction signal of the current block. If the prediction signalgenerated using a neighboring MV uses samples from a different face thanthat of the current block or sub-block, OBMC may be disabled for thatMV.

For example, a block or sub-block may be located below a facediscontinuity. A left boundary of the block or sub-block may beadjusted. If the prediction signal is generated using a left neighboringmotion vector (e.g., which may come from the same face as the currentblock or sub-block) and/or uses samples from above the facediscontinuity, OBMC may be disabled for the left block or sub-blockboundary.

In examples, OBMC for blocks (or sub-blocks) that are located next to aface discontinuity may be disabled (e.g., completely disabled). Inexamples, OBMC for blocks (or sub-blocks) that are crossed by a facediscontinuity may be disabled (e.g., completely disabled).

A deblocking filter may be applied at face discontinuities.

Deblocking of the block boundaries that are within the proximity of aface discontinuity may be skipped when one or more (e.g., all) samplesused in a deblocking filter are not located on the same side of the facediscontinuity. For example, if a vertical block boundary is within theproximity of a vertical face discontinuity such that one or more (e.g.,all) samples used in the deblocking filter are not located on the sameside of the face discontinuity, the deblocking filter may be disabledacross this block boundary. If a horizontal block boundary is within theproximity of a horizontal face discontinuity such that one or more(e.g., all) samples used in the deblocking filter are not located on thesame side of the face discontinuity, the deblocking filter may bedisabled across this block boundary.

A sample adaptive offset (SAO) filter may be applied at facediscontinuities. One or more categories in edge offset mode in SAO forwhich the samples used in gradient computations are on two differentsides of a face discontinuity may be disabled. For example, if a facediscontinuity is located above or below a current sample position, thevertical and two diagonal categories may be disabled for that sampleposition. If a face discontinuity is located on the left side of or onthe right side of the current sample position, the horizontal and twodiagonal categories may be disabled for that sample position. Inexamples, the edge offset mode in SAO may be disabled (e.g., completelydisable) for samples that are located next to a face discontinuity.

An adaptive loop filter (ALF) may be applied at face discontinuities.ALF may skip sample locations where the largest filter crosses a facediscontinuity. For example, ALF may skip sample locations where thesamples used in the filtering process are on two different sides of aface discontinuity. For the luma component, which may use up to a 9×9diamond filter (e.g., see FIG. 16(c)), ALF may be disabled for sampleslocated within four samples of a face discontinuity. For the chromacomponents, which may use (e.g., only use) a 5×5 diamond filter (e.g.,see FIG. 16(a)), ALF may be disabled for samples located within twosamples of a face discontinuity.

In examples, ALF may be disabled (e.g., completely disabled) for blocksthat are located next to a face discontinuity and/or for blocks thatinclude a face discontinuity. Disabling ALF may allow a decoder toperform a determination (e.g., of whether ALF is on or off) at the blocklevel. ALF may be adapted (e.g., turned on/off) at the picture-leveland/or block-level. ALF may be turned off for a given block, for examplewhen the block is affected by a face discontinuity (e.g., the block iscrossed by a face discontinuity or is adjacent to a face discontinuity).Block-level signaling may be skipped for the block, and ALF may beinferred to be off for that block.

The ALF classification process may skip one or more sample locationsand/or blocks of sample locations where ALF filtering may be disabled.For example, the ALF classification may skip a sample location becausethe sample location is affected by a face discontinuity (e.g., thesamples used in the classification process at that sample location areon two different sides of a face discontinuity). ALF classification mayskip a block if one or more samples within the block are affected by aface discontinuity. ALF classification may be performed on 2×2 blockunits.

FIG. 25A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word DFT-Spread OFDM (ZT UW DTS-s OFDM), unique word OFDM(UW-OFDM), resource block-filtered OFDM, filter bank multicarrier(FBMC), and the like.

As shown in FIG. 25A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a RAN104/113, a CN 106/115, a public switched telephone network (PSTN) 108,the Internet 110, and other networks 112, though it will be appreciatedthat the disclosed embodiments contemplate any number of WTRUs, basestations, networks, and/or network elements. Each of the WTRUs 102 a,102 b, 102 c, 102 d may be any type of device configured to operateand/or communicate in a wireless environment. By way of example, theWTRUs 102 a, 102 b, 102 c, 102 d, any of which may be referred to as a“station” and/or a “STA”, may be configured to transmit and/or receivewireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watchor other wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 1061115, the Internet110, and/or the other networks 112. By way of example, the base stations114 a, 114 b may be a base transceiver station (BTS), a Node-B, an eNodeB, a Home Node B, a Home eNode B, a gNB, a NR NodeB, a site controller,an access point (AP), a wireless router, and the like. While the basestations 114 a, 114 b are each depicted as a single element, it will beappreciated that the base stations 114 a, 114 b may include any numberof interconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104/113, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, etc. The base station 114 a and/or the base station 114 b may beconfigured to transmit and/or receive wireless signals on one or morecarrier frequencies, which may be referred to as a cell (not shown).These frequencies may be in licensed spectrum, unlicensed spectrum, or acombination of licensed and unlicensed spectrum. A cell may providecoverage for a wireless service to a specific geographical area that maybe relatively fixed or that may change over time. The cell may furtherbe divided into cell sectors. For example, the cell associated with thebase station 114 a may be divided into three sectors. Thus, in oneembodiment, the base station 114 a may include three transceivers, i.e.,one for each sector of the cell. In an embodiment, the base station 114a may employ multiple-input multiple output (MIMO) technology and mayutilize multiple transceivers for each sector of the cell. For example,beamforming may be used to transmit and/or receive signals in desiredspatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104/113 and the WTRUs 102 a,102 b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 115/116/117 using wideband CDMA (WCDMA).WCDMA may include communication protocols such as High-Speed PacketAccess (HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-SpeedDownlink (DL) Packet Access (HSDPA) and/or High-Speed UL Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using New Radio (NR).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., a eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b.102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 25A may be a wireless router, Home NodeB, Home eNode B, or access point, for example, and may utilize anysuitable RAT for facilitating wireless connectivity in a localized area,such as a place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 25A, the base station 114 b may have a direct connectionto the Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106/115.

The RAN 104/113 may be in communication with the CN 106/115, which maybe any type of network configured to provide voice, data, applications,and/or voice over internet protocol (VoIP) services to one or more ofthe WTRUs 102 a, 102 b, 102 c, 102 d. The data may have varying qualityof service (QoS) requirements, such as differing throughputrequirements, latency requirements, error tolerance requirements,reliability requirements, data throughput requirements, mobilityrequirements, and the like. The CN 106/115 may provide call control,billing services, mobile location-based services, pre-paid calling.Internet connectivity, video distribution, etc., and/or performhigh-level security functions, such as user authentication. Although notshown in FIG. 25A, it will be appreciated that the RAN 104/113 and/orthe CN 106/115 may be in direct or indirect communication with otherRANs that employ the same RAT as the RAN 1041113 or a different RAT. Forexample, in addition to being connected to the RAN 104/113, which may beutilizing a NR radio technology, the CN 106/115 may also be incommunication with another RAN (not shown) employing a GSM, UMTS, CDMA2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106/115 may also serve as a gateway for the WTRUs 102 a, 102 b,102 c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104/113 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 25A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 25B is a system diagram illustrating an example WTRU 102. As shownin FIG. 25B, the WTRU 102 may include a processor 118, a transceiver120, a transmit/receive element 122, a speaker/microphone 124, a keypad126, a display/touchpad 128, non-removable memory 130, removable memory132, a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 25Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 25B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors, the sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor; an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, and/ora humidity sensor.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) anddownlink (e.g., for reception) may be concurrent and/or simultaneous.The full duplex radio may include an interference management unit toreduce and or substantially eliminate self-interference via eitherhardware (e.g., a choke) or signal processing via a processor (e.g., aseparate processor (not shown) or via processor 118). In an embodiment,the WRTU 102 may include a half-duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for either the UL (e.g., for transmission) or thedownlink (e.g., for reception)).

FIG. 25C is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 25C, the eNode-Bs160 a, 160 b, 160 c may communicate with one another over an X2interface.

The CN 106 shown in FIG. 25C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (or PGW) 166. While each of the foregoing elements are depictedas part of the CN 106, it will be appreciated that any of these elementsmay be owned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a. 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 20A-D as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have an access or an interface to a DistributionSystem (DS) or another type of wired/wireless network that carriestraffic in to and/or out of the BSS. Traffic to STAs that originatesfrom outside the BSS may arrive through the AP and may be delivered tothe STAs. Traffic originating from STAs to destinations outside the BSSmay be sent to the AP to be delivered to respective destinations.Traffic between STAs within the BSS may be sent through the AP, forexample, where the source STA may send traffic to the AP and the AP maydeliver the traffic to the destination STA. The traffic between STAswithin a BSS may be considered and/or referred to as peer-to-peertraffic. The peer-to-peer traffic may be sent between (e.g., directlybetween) the source and destination STAs with a direct link setup (DLS).In certain representative embodiments, the DLS may use an 802.11e DLS oran 802.11z tunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS)mode may not have an AP, and the STAs (e.g., all of the STAs) within orusing the IBSS may communicate directly with each other. The IBSS modeof communication may sometimes be referred to herein as an “ad-hoc” modeof communication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width via signaling.The primary channel may be the operating channel of the BSS and may beused by the STAs to establish a connection with the AP. In certainrepresentative embodiments, Carrier Sense Multiple Access with CollisionAvoidance (CSMA/CA) may be implemented, for example in in 802.11systems. For CSMA/CA, the STAs (e.g., every STA), including the AP, maysense the primary channel. If the primary channel is sensed/detectedand/or determined to be busy by a particular STA, the particular STA mayback off. One STA (e.g., only one station) may transmit at any giventime in a given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20 MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac, 802.11afsupports 5 MHz, 10 MHz and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications, such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode), transmitting to the AP, the entire available frequency bands maybe considered busy even though a majority of the frequency bands remainsidle and may be available.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 25D is a system diagram illustrating the RAN 113 and the CN 115according to an embodiment. As noted above, the RAN 113 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 113 may also be in communication with theCN 115.

The RAN 113 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 113 may include any number of gNBs whileremaining consistent with an embodiment. The gNBs 180 a, 180 b, 180 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the gNBs 180 a, 180 b, 180 c may implement MIMO technology. For example,gNBs 180 a, 108 b may utilize beamforming to transmit signals to and/orreceive signals from the gNBs 180 a, 180 b, 180 c. Thus, the gNB 180 a,for example, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an embodiment,the gNBs 180 a, 180 b, 180 c may implement carrier aggregationtechnology. For example, the gNB 180 a may transmit multiple componentcarriers to the WTRU 102 a (not shown). A subset of these componentcarriers may be on unlicensed spectrum while the remaining componentcarriers may be on licensed spectrum. In an embodiment, the gNBs 180 a,180 b, 180 c may implement Coordinated Multi-Point (CoMP) technology.For example, WTRU 102 a may receive coordinated transmissions from gNB180 a and gNB 180 b (and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containingvarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b. 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, dual connectivity, interworkingbetween NR and E-UTRA, routing of user plane data towards User PlaneFunction (UPF) 184 a, 184 b, routing of control plane informationtowards Access and Mobility Management Function (AMF) 182 a, 182 b andthe like. As shown in FIG. 25D, the gNBs 180 a, 180 b, 180 c maycommunicate with one another over an Xn interface.

The CN 115 shown in FIG. 25D may include at least one AMF 182 a, 182 b,at least one UPF 184 a,184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whileeach of the foregoing elements are depicted as part of the CN 115, itwill be appreciated that any of these elements may be owned and/oroperated by an entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different PDU sessions with differentrequirements), selecting a particular SMF 183 a, 183 b, management ofthe registration area, termination of NAS signaling, mobilitymanagement, and the like. Network slicing may be used by the AMF 182 a,182 b in order to customize CN support for WTRUs 102 a, 102 b, 102 cbased on the types of services being utilized WTRUs 102 a, 102 b, 102 c.For example, different network slices may be established for differentuse cases such as services relying on ultra-reliable low latency (URLLC)access, services relying on enhanced massive mobile broadband (eMBB)access, services for machine type communication (MTC) access, and/or thelike. The AMF 162 may provide a control plane function for switchingbetween the RAN 113 and other RANs (not shown) that employ other radiotechnologies, such as LTE, LTE-A, LTE-A Pro, and/or non-3GPP accesstechnologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN115 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 115 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating UE IP address,managing PDU sessions, controlling policy enforcement and QoS, providingdownlink data notifications, and the like. A PDU session type may beIP-based, non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 113 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering downlink packets, providing mobility anchoring, and thelike.

The CN 115 may facilitate communications with other networks. Forexample, the CN 115 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 115 and the PSTN 108. In addition, the CN 115may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneembodiment, the WTRUs 102 a, 102 b, 102 c may be connected to a localData Network (DN) 185 a, 185 b through the UPF 184 a, 184 b via the N3interface to the UPF 184 a, 184 b and an N6 interface between the UPF184 a, 184 b and the DN 185 a, 185 b.

In view of FIG. 25A-D, and the corresponding description of FIG. 25A-1D, one or more, or all, of the functions described herein with regardto one or more of WTRU 102 a-d, Base Station 114 a-b, eNode-B 160 a-c,MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184 a-b, SMF183 a-b, DN 185 a-b, and/or any other device(s) described herein, may beperformed by one or more emulation devices (not shown). The emulationdevices may be one or more devices configured to emulate one or more, orall, of the functions described herein. For example, the emulationdevices may be used to test other devices and/or to simulate networkand/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or may performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

1-15. (canceled)
 16. A method comprising: obtaining a virtual boundaryloop filter disable indicator configured to indicate that a loopfiltering is to be disabled across a virtual boundary in a picture;based on the virtual boundary loop filter disable indicator configuredto indicate that the loop filtering is to be disabled across the virtualboundary in the picture, obtaining a virtual boundary positionindicator, wherein the virtual boundary position indicator is configuredto indicate a position along an axis that is associated with a virtualboundary in the picture where the loop filtering is to be disabled;based on the obtained virtual boundary position indicator, determining aposition of the virtual boundary in the picture where the loop filteringis to be disabled; and disabling the loop filtering across thedetermined position of the virtual boundary in the picture.
 17. Themethod of claim 16, wherein the virtual boundary position indicator isfurther configured to indicate a number of virtual boundaries in thepicture.
 18. The method of claim 16, wherein the virtual boundaryposition indicator is further configured to indicate a number of virtualboundaries where the loop filtering is to be disabled in the picture.19. The method of claim 16, wherein the virtual boundary positionindicator is configured to indicate a start position and an end positionof at least one virtual boundary.
 20. The method of claim 16, whereinthe virtual boundary position indicator comprises at least one of avertical virtual boundary position indicator or a horizontal virtualboundary position indicator, wherein the vertical virtual boundaryposition indicator is configured to indicate a position along ahorizontal axis that is associated with a vertical virtual boundary inthe picture where the loop filtering is to be disabled, and wherein thehorizontal virtual boundary position indicator is configured to indicatea position along a vertical axis that is associated with a horizontalvirtual boundary in the picture where the loop filtering is to bedisabled.
 21. The method of claim 16, wherein the picture comprises aframe-packed picture having a plurality of faces, and the virtualboundary in the picture comprises a face boundary in the picture. 22.The method of claim 16, wherein the virtual boundary loop filter disableindicator is obtained at a sequence parameter set (SPS) level.
 23. Themethod of claim 16, wherein the loop filtering comprises at least one ofadaptive loop filter (ALF), deblocking filter, or sample adaptive offset(SAO) filter.
 24. The method of claim 16, wherein the picture isassociated with a 360 degree video.
 25. An apparatus comprising: aprocessor configured to: obtain a virtual boundary loop filter disableconfigured to indicate, that a loop filtering is to be disabled across avirtual boundary in a picture; based on the virtual boundary loop filterdisable indicator configured to indicate that the loop filtering is tobe disabled across the virtual boundary in the picture, obtain a virtualboundary position indicator, wherein the virtual boundary positionindicator is configured to indicate a position along an axis that isassociated with a virtual boundary in the picture where the loopfiltering is to be disabled; based on the obtained virtual boundaryposition indicator, determine a position of the virtual boundary in thepicture where the loop filtering is to be disabled; and disable the loopfiltering across the determined position of the virtual boundary in thepicture.
 26. The apparatus of claim 25, wherein the virtual boundaryposition indicator is further configured to indicate a number of virtualboundaries in the picture.
 27. The apparatus of claim 25, wherein thevirtual boundary position indicator is further configured to indicate anumber of virtual boundaries where the loop filtering is to be disabledin the picture.
 28. The apparatus of claim 25, wherein the virtualboundary position indicator is configured to indicate a start positionand an end position of at least one virtual boundary.
 30. The apparatusof claim 25, wherein the virtual boundary position indicator comprisesat least one of a vertical virtual boundary position indicator or ahorizontal virtual boundary position indicator, wherein the verticalvirtual boundary position indicator is configured to indicate a positionalong a horizontal axis that is associated with a vertical virtualboundary in the picture where the loop filtering is to be disabled, andwherein the horizontal virtual boundary position indicator is configuredto indicate a position along a vertical axis that is associated with ahorizontal virtual boundary in the picture where the loop filtering isto be disabled.
 31. The apparatus of claim 25, wherein the picturecomprises a frame-packed picture having a plurality of faces, and thevirtual boundary in the picture comprises a face boundary in thepicture.
 32. The apparatus of claim 25, wherein the virtual boundaryloop filter disable indicator is obtained at a sequence parameter set(SPS) level.
 33. The apparatus of claim 25, wherein the loop filteringcomprises at least one of adaptive loop filter (ALF), deblocking filter,or sample adaptive offset (SAO) filter.